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simplify the snapshots and extract the physics all snapshots are independent of each other simplifies the computing, embarrassingly parallel there is lots of noise to be subtracted need to understand precisely the environment (detectors, accelerator, etc.) is the measured effect really the underlying basic physics or just an artifact from the measurement itself ?! TasksTasks

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Software glue management of the basic hardware and software : installation, configuration and monitoring system Which version of Linux ? How to upgrade the software ? What is going on in the farm ? Load ? Failures ? management of the processor computing resources : Batch system (LSF from Platform Computing) Where are free processors ? How to set priorities between different users ? sharing of the resources ? How are the results coming back ? management of the storage (disk and tape) : CASTOR (CERN developed Hierarchical Storage Management system) Where are the files ? How can one access them ? How much space is available ?

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~120000 processors Resources for Computing CERN can only contribute ~15% of these resource need a world-wide collaboration CERN can only contribute ~15% of these resource need a world-wide collaboration ~100000 disks today

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Use the Grid to unite computing resources of particle physics institutes around the world The World Wide Web provides seamless access to information that is stored in many millions of different geographical locations The Grid is an infrastructure that provides seamless access to computing power and data storage capacity distributed over the globe Solution: the Grid Tim Berners-Lee invented the World Wide Web at CERN in 1989

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Grid history Name Grid chosen by analogy with electric power grid (Foster and Kesselman 1997) Vision: plug-in computer for processing power just like plugging in toaster for electricity. Concept has been around for decades (distributed computing, metacomputing) Key difference with the Grid is to realize the vision on a global scale.

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I want to analyze the LHC measurements Where are the data ? How do I access them ? Where is a free computer ? How do I get the results back ? There are many different centers ! Each one with different hardware and software ! ? ? ? ? ? Am I allowed to work in this center ?

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How does the Grid work? It relies on advanced software, called middleware. Middleware automatically finds the data the scientist needs, and the computing power to analyse it. Middleware balances the load on different resources. It also handles security, accounting, monitoring and much more.

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DBS DLS Dataset Bookeeping System: What kind of data exists? Data Location Service: Where is the data? Local Mass Storage System physical location of files at the site RAW data at CERN, Geneva, Switzerland copy1 at Fermilab, Chicago, USA sub-sample2 at GSI, Darmstadt, Germany sub-sample5 at ASCG, Taipei, Taiwan ………… I want to analyze all events with one muon from run 2345 on the 29 th of July 2008 HSM WMS WN Computer Center GSI, Darmstadt, Germany Computer Center GSI, Darmstadt, Germany Work Load Management System decide on best match of CPU resources and data location Work Load Management System decide on best match of CPU resources and data location task Worker Nodes result